airDRIVE - AN OVERVIEW.
airSOUND® airDRIVE: a new amplification technology for significantly improved audio reproduction
Traditionally, amplifiers have been designed by amplifier engineers, and loudspeakers by loudspeaker engineers; the amplifiers produced are good, as amplifiers, and the loudspeakers work well as loudspeakers, but little thought has ever been given to optimising the combination of an amplifier and a loudspeaker.
Research work at airSOUND has shown that comparing the acoustic output to the electrical input and controlling the dynamic current in the loudspeaker coil can dramatically improve the performance of many moving-coil loudspeakers.
An airDRIVE system is an amplifier loudspeaker combination that successfully combines the amplifier and loudspeaker in a single system and eliminates the errors and distortions within the loudspeaker due to conventional ‘constant voltage’ drive.
(In a conventional system, the ultra-low impedance output of a power amplifier produces a constant voltage output to the loudspeaker. The dynamic impedance of the loudspeaker coil varies with the instantaneous loads applied to the cone, both through inertial forces in the loudspeaker materials, and through dynamic back-pressures from the loudspeaker enclosure or acoustic environment, so the current in the coil and therefore the audio output is adversely affected by the impedance variations.)
A principal advantage of airDRIVE is in the reproduction of transient information. Transient audio signals and other sudden excursions induce changes in the dynamic impedance of the loudspeaker coil, and because within airDRIVE the coil is a part of the closed system, the amplifier produces massive additional force so that the loudspeaker is made to respond with precision.
The basic principle of pure current amplification (one of the roots of airDRIVE) is widely used for low frequency power amplification for vibration test equipment, but it's implementation with loudspeakers poses a number of significant difficulties that have prevented any extensive use of the system, and exploitation of the theoretical advances offered for audio reproduction.
In the orbitsound T21, airSOUND is specifically claiming the first application of airDRIVE where the distorting effect of mass and inertia of the loudspeaker is minimised by the driving current itself, and where the acoustic conditions of a room have a modifying effect on the amplifier/loudspeaker combination to produce a more linear relationship between the acoustic pressures in the room and the incoming audio voltage.
Advantages of airSOUND airDRIVE™:- Significantly reduced harmonic distortion in the acoustic output.
- Improvement in transient response, resulting in far greater clarity and audio fidelity.
- Extended frequency response both at low and high frequencies.
- It is a loudspeaker/amplifier combination that reacts to its environment.
- airDRIVE forms the subject of UK patent application 0821327.4 dated Nov 2008.
